This invention relates to a method for producing boxes of foil pouches containing a product, such as a dry food product, wherein each box is to contain a prescribed number of pouches. The invention also relates to a system for implementing the above method.
In known machines for packaging dry food products such as soup mixes, for example, in foil pouches, an elongate strip of foil, typically a plastic, paper and foil laminate, is drawn over and folded by a plow to form a U-shaped trough open at the top, the confronting layers of foil are then heat-sealed at spaced locations along the length and then severed along the seal lines to form individual pouches each closed at the bottom and sealed along vertical side edges. The empty pouches are transported along a path beneath a succession of hoppers from which measured quantities of different ingredients are dispensed, and then to sealing apparatus at which the open top of the filled pouch is heatsealed. A specified number of pouches are inserted in a box in which the product is to be retailed, the number being determined by the nature of the product; typically, each box may contain two, three or four pouches, although for some products there may be only one pouch per box. After the specified number of pouches have been inserted, the box is automatically sealed and transported to a carton for storage and shipment.
For obvious marketing reasons no short count boxes are permitted, and in order that the consumer not be given more than for which he or she has paid a box should not contain more than the specified number of pouches. In the known Peco system for detecting whether a pouch is missing from a box intended to contain two foil pouches, an alternating magnetic field is applied through each box and the detected output, which is a measure of the field absorbed by the foil pouches contained in the box, is balanced against a DC reference voltage. This system is only capable of detecting whether one out of two pouches is missing from a box, and produces correct results only for the foil thickness to which it is initially balanced; consequently, not uncommon variations in foil thickness cause erroneous results. Also, because the Peco system is single-ended, it is unable to detect one pouch missing from a box which is supposed to contain three or four pouches.